Wireless communication standards such a CDMA First Evolution-Data Only (1xEV-DO) provide for multiple carriers to increase capacity of the system as well as provide different levels and types of services. For systems with multiple carriers, balancing the load on the carriers so the system resources may be fully utilized is desirable. The system resources may be considered as having two parts, traffic channel resources and control channel resources. For example, the access channel and paging channel of each carrier are part of the control channel resources.
Depending on the system organization, the carriers are divided into two or more classes. For example, there are several wireless communication systems capable of providing broadcast/multicast services (BCMCS), and carriers that carry BCMCS may be one class while carriers that do not carry BCMCS may be a different class.
FIG. 1 illustrates a conventional wireless system, for example, an EV-DO system 100 supporting multiple carriers. An Access Terminal (AT) (also known as a mobile terminal or a mobile station) 10 may be connected with a plurality of Access Nodes (ANs) 20. The ANs 20 are connected to a Radio Network Controller (RNC) 30. The RNC 30 provides services and coordination between the ATs 10 and external systems, for example, a Packet Data Service Node (PDSN) 50. The system 100 may include a number of RNCs 30, and each RNC 30 may have a plurality of ANs 20 associated therewith. The PDSN 50 is a termination node and may be connected to an Internet 40 or other systems capable of providing data services to the AT 10. The PDSN 50 may also be connected to a Broadcast/Multicast Service (BCMCS) content server 60. The BCMCS content server 60 may provide broadcast data, which may include multi-media data, such as text, audio, picture, streaming video, Internet protocol packets, etc. to the AT 10. The content is typically generated and provided to the ATs that subscribe to a particular service over a broadcast channel of the wireless communication system.
As is well-known, when an AT 10 enters the coverage area of an RNC 30, the AT 10 negotiates a session setup. In this context, the AT 10 is in the idle state, and the session simply refers to the duration the AT 10 is in the coverage area of the RNC 30. According to the EV-DO Rev A standard, a traffic channel is established between the AT 10 and the RNC 30, and the session setup is negotiated through the traffic channel. During the session setup, parameters are shared between AT 10 and RNC 30. The AT 10 notifies the RNC 30 of its capabilities, etc. For example, the AT 10 may notify the RNC 30 whether it is BCMCS enabled or not, the AT 10 may notify the RNC 30 of its electronic serial number (ESN), etc. The RNC 30 notifies the AT 10 of the multiple carriers supported by the ANs 20 associated with the RNC 30 and the class of each carrier. Based on the information from the AT 10, the RNC 30 also assigns a class to the AT 10. For example, if the carriers are divided into a BCMCS class and a non-BCMCS class, then if the AT is BCMCS enabled, the AT is assigned the BCMCS class.
Based on the assigned class, the AT 10 hashes onto one of the carriers having the same class as the serving carrier. Typically, each AT 10 hashes to a carrier using a hashing algorithm based on a unique identifier of the AT 10 such as an electronic serial number (ESN). The RNC 30 performs the same hashing algorithm to determine the selection made by the AT 10. The AT 10 will then monitor the control/paging channels of the serving carrier. This is often referred to as camping onto the carrier. The AT 10 will also access the wireless communication system over the access channel of the serving carrier.